Glycoprotein receptors to wheat germ agglutinin on the surface of murine macrophages.

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Abstract
Peritoneal macrophages elicited in various ways exhibited marked wheat germ agglutinin (WGA)-dependent cytolytic activity against MM46 cells [nearly 100% lysis at effector to target ratio (E/T)=40], while macrophage cell lines J774.1 and WEHI-3 cells showed less activity (-25% at E/T=0.63-2.5) and no cytolysis (E/T=40), respectively. Studies on the kinetics of WGA-binding showed that peritoneal macrophages had an association constant (Ka) of 0.09-0.18×106 M-1 and the number of their binding sites (N) was 2-7.7×107/cell, while the Ka and N values of J774.1 and WEHI-3 cells were 1.2×106 M-1 and 4.1×107/cell and 0.6×106 M-1 and 5.4×107/cell, respectively. On the other hand, cytolytic target MM46 cells showed values of 0.27×106 M-1 and 1.8×108/cell. Lower affinities and moderate numbers of binding sites coincided with the efficient WGA-dependent cytolytic activities of the effector cells. The surface of peritoneal macrophages and J774.1 and MM46 cells was iodinated, the cells lysed, the lysates fractionated on a WGA-Sepharose column and the WGA-binding surface-glycoproteins in GlcNAc-specific fractions of the eluate were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Peritoneal macrophages gave three major bands of 153 kilo dalton (kDa), 140 and 90 kDa proteins, whereas J774.1 and MM46 cells both gave 6 bands of very similar molecular weights and intensities that were quite unlike those of peritoneal macrophages. These results suggest that the three major WGA-binding glycoproteins on peritoneal macrophages are involved in adherence and the lytic process in WGA-dependent macrophage-mediated cytolysis.
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